Design and Planning

Highway Planting Research

This study developed and tested various California native grass species grown and installed using various planting mediums and installation techniques at five different locations throughout the state. A key finding was that native grasses can be developed as a sustainable roadside vegetation community; however, there is a limited number of native grass species that will survive under the harsh conditions typical on Caltrans roadsides.

Integrated Vegetation Management (IVM) techniques were used in the Bear Creek Botanical management Area to successfully restore native vegetation and habitat.

The ecological value of the Bear Creek BMA has been greatly enhanced by the Integrated Vegetation Management IVM program. The presence of noxious weeds declined over the five years of the study and created conditions that allowed native plants to flourish. Yellow starthistle was reduced by 99% in the core grassland area; the dense yellow starthistle canopies, high seedlings densities, and thick thatch that characterized infestations were eliminated. Intensive control efforts further reduced yellow starthistle and barb goatgrass, bringing them close to eradication. Purple starthistle and giant reed were eradicated and tamarisk and perennial pepperweed were nearly been eliminated. Successful IVM practices were documented, emphasizing reduced herbicide use, with judicious spot applications as part of a total program.

Caltrans funded and administered a research project performed by The Montana State University. The purpose of this research was to develop methods to grow and plant native grass sod in an economically viable and commercially available way. Native grass sod provides immediate as well as long-term protection of bare soil, protecting water quality.

A review of the basic science and practice of legume seed inoculation was performed to ascertain whether documented evidence exists to indicate that legume inoculation for nitrogen-augmentation is both consistently reliable and quantifiable. The recommendation of this study is that the Department abandon the practice of seed inoculation. Routine fertility testing, stockpiling of topsoil and other means to augment nitrogen availability will likely provide greater long-term benefits.

This report contains a number of experiments designed to study the competitive interactions between herbaceous species used in erosion control seeding. The results of these experiments suggest that within an herbaceous plant community, species that use resources differently in space and time create more stable plant communities than species with more similar resource use patterns.